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I'm using an 18v makita hammer drill with a 3/16" Bosch blue granite turbo concrete bit to drill 2" deep holes into concrete-filled cinder blocks. With a fresh bit, it takes about 15 seconds to drill a hole. By the 4th hole, it slows to a crawl and it takes 2-3 minutes to drill a complete hole. After the 5th hole, the bit is completely shot and I have to get a new bit. I've gone through half a dozen bits now, trying to discover what I'm doing wrong - and I have no idea.

The hammering action of the drill isn't activating, so i'm losing all of the impact potential - I can't really apply any more force than I am already, as the drilling is happening over-head at an awkward angle... Any idea if there's a reason the bits dull so quickly? Is this a better job for an impact drill?

I should also say that I can't notice any visible difference on the tip of the bit - it doesn't look blunted, or marred, which is part of why it's so puzzling. I don't have a means to sharpen it, but just from visual inspection it looks OK

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    Hard to be certain, but I wonder if you are overheating the drill bit - too much speed, not enough pressure. Try using a lower speed...? Dip it in water from time to time...
    – Ecnerwal
    Jan 22, 2020 at 23:46
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    Why don't you try it with a properly operating hammer drill?
    – jwh20
    Jan 22, 2020 at 23:53
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    Last time I had to do that, IIRC I went through 2 bits for 30 holes, and I didn't have a hammer drill. However it was a corded drill geared for low RPM (which I normally hate in a drill, but it served here).
    – Harper - Reinstate Monica
    Jan 23, 2020 at 1:55
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    @bornfromanegg Depending on location it is indeed called an impact drill and that's the same as what others call a hammer drill or knock drill.
    – Mast
    Jan 23, 2020 at 12:14
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    Note that carbide-tipped SDS bits don't need to seem sharp (by look or feel) to work well when hammer action is employed. The teeth can be well-rounded and do almost as good a job as when new. It's when they lose the carbide teeth or overheat and mushroom that they become worthless.
    – isherwood
    Jan 23, 2020 at 19:03

5 Answers 5

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The hammering action of the drill isn't activating

So the bit is overheating due to friction. It is supposed to hammer the material you're drilling into dust then evacuate it, not rub it off through friction.

You have to activate the hammer action.

Pretty much the only use cases for not using the hammer action are when drilling into ceramic tile to avoid breaking it, or drilling into plasterboard or other soft materials where hammering will smash through and make a crater on the other side...

Is this a better job for an impact drill?

Advantages of cordless hammer drill's are

  1. Light weight.

  2. Convenience, you can drill the hole and drive the screw with the same tool.

  3. It works for a few small holes (like less than 6mm diameter) in easy to drill materials like brick, cinderblock, soft stone (limestone), etc.

Drawbacks: noisy and underpowered, slow/useless on tough materials (hard stone, concrete especially if it contains rebar).

If you want to make lots of holes, or diameters like 10mm and up, or drill into tough stuff, a rotary hammer with SDS+ bits will be a LOT faster.

Don't get an impact driver for drilling, impact drivers are for bolts and tough screws, not for drilling.

I don't have a means to sharpen it, but just from visual inspection it looks OK

It's tungsten carbide, you can't really sharpen it. Besides, it doesn't need to be really sharp, it's basically a tiny hammer with a blunt point.

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    Usually if you want to drill holes in hard stuff you need SDS shank bits on a hammer drill, nothing else except dynamite can make holes as fast as them. I once borrowed a proper hammer drill with SDS shanks and after doing what needed done, I immediately bought one for myself. No more endless drilling, the hammer drill sinks the bits into concrete so fast and smooth that it is a mix of scary and arousing.
    – Stian
    Jan 23, 2020 at 9:37
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    Is this a better job for an impact drill? I think you're talking about two different things. I think OP means an impact driver (rotary impact), which is definitely not what you want for driving a masonry bit (axial impact - hammer).
    – J...
    Jan 23, 2020 at 17:10
  • @J... Agreed, different tool. An impact driver is for removing stubborn machine bolts and nuts. A hammer drill is for masonry. Answer needs to be updated to address OP's confusion, rather than conflate the terms.
    – Rich
    Jan 23, 2020 at 17:14
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    @Rich Indeed - even most cordless "drills" now are also compact impact drivers - not for machine bolts or anything like that necessarily, but even just for driving deck screws, etc, which I think is the type of tool that OP is talking about.
    – J...
    Jan 23, 2020 at 17:38
  • This is right. It's very easy to melt smaller bits (3/16" and under) even when the hammer is working. It's a good strategy to replace bits after every few holes and allow them to cool.
    – isherwood
    Jan 23, 2020 at 19:01
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An SDS-plus hammer drill will make holes very fast using a bit that starts hardly sharp and rapidly becomes completely dull. It really doesn't care, because it's a pneumatic hammer action and the rotary action is just to clear away the dust. (It also works with masonry chisel bits if you turn the rotation off.

An "ordinary" hammer/non-hammer drill had a very inferior hammer action (when engaged). I'd have expected it to be OK with 3/16 into cinder blocks and soft bricks, but on solid concrete or hard bricks, not much or no good. I never purchased expensive bits for use with such a drill. I used cheap-as-chips Chinese carbide tipped drills sold in 6-packs and threw them away when they wore out, which they did often.

When I moved to a house built of natural stone outside and inside, the hardest bricks I have ever encountered, I gave up and bought Bosch's cheapest SDS_plus hammer drill. It was money very well spent.

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    The rotary action does more than just clear the dust, (which you have to help it do or it'll get stuck: keep pulling it out and going back in); just like a hand held star drill that you have to rotate after each strike. - SDS rotatory chipping hammers: best money you'll ever spend, +1. Some of my bits were used, are +20yo, and they dgaf about it.
    – Mazura
    Jan 24, 2020 at 3:50
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The hammering action of the drill linked in the picture doesn't really need anything more than turning the dial to the hammer setting - it doesn't selectively "activate." It should be pretty noticeable but nothing that's going to bounce you out of your shorts.

The mechanism is usually something like two plastic poker chips rotating, which gives you some vibration, but not true hammering action like a rotary hammer.

It's likely you're just heating up the bits and ruining them quickly.

If you're setting the dial to hammer and exerting decent pressure, it's the drill that's the problem.

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Make sure you have not accidentally set the drill in reverse mode. When the bit rotates the wrong way it causes the bit to heat up and wear out. Something similar to this happened to a friend and to myself.

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Go to harbor freight and get an SDS or SDS max. Any consumer/pro drill that has a 'hammer' mode will stink compared to a proper tool. I've gone through much harder material using the SDS-Max I bought for 100$ whereas I would ruin bits with my makita or Milwaukee.

So yes, you're over heating the bit and it isn't removing the material right.

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    OP says the hammer action isn't even activating ... buying yet another tool isn't going to fix their inability to select the correct mode. In my experience, any cheap hammer drill is perfectly sufficient for household projects. At a slow-enough speed they go in like butter, and you'll lose the bits in the shed before they get blunt...
    – Rich
    Jan 23, 2020 at 17:22
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    I bought an sds hammer drill from harbor freight last year. I drilled nineteen 5/8" holes through 6-8" of concrete with a single bit. I think that's evident enough that the cheap HF tool will do the job for him just fine.
    – Phaelax z
    Jan 23, 2020 at 18:04
  • Doesn't matter- the hand drill isn't going to hammer enough to do what he's described. It'll chew up batteries and not make much progress. Right tool, right results.
    – J.Hirsch
    Jan 24, 2020 at 13:46

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